From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Fri, 4 Nov 2016 22:04:34 +0000 (-0600)
Subject: Improved testAppendSBuf to actually test SBuf::append() optimization.
X-Git-Tag: SQUID_4_0_17~39
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5534a101594a15ebe2ac67ceea7ad56b0e7cf4d4;p=thirdparty%2Fsquid.git

Improved testAppendSBuf to actually test SBuf::append() optimization.

... rather than to test SBuf::id preservation across assignments
[currently used by that optimization].

Trunk r14911 talks about bitwise object copy but making sure that SBuf
has a working assignment operator is an issue unrelated to append() and
its optimization. Besides, it is not really the prohibited by C++
bitwise copy that we might worry about but the default member-wise
assignment that we may forget to customize.
---

diff --git a/src/tests/testSBuf.cc b/src/tests/testSBuf.cc
index 4f29d29550..e80ca60be2 100644
--- a/src/tests/testSBuf.cc
+++ b/src/tests/testSBuf.cc
@@ -151,20 +151,22 @@ testSBuf::testEqualityTest()
 void
 testSBuf::testAppendSBuf()
 {
-    SBuf empty, s1(fox1), s2(fox2);
-    auto oldId1 = s1.getId();
-    s1.append(s2);
-    CPPUNIT_ASSERT_EQUAL(s1,literal);
+    const SBuf appendix(fox1);
+    const char * const rawAppendix = appendix.rawContent();
 
-    // SBuf docs state that InstanceId does not change
-    CPPUNIT_ASSERT_EQUAL(oldId1, s1.getId());
+    // check whether the optimization that prevents copying when append()ing to
+    // default-constructed SBuf actually works
+    SBuf s0;
+    s0.append(appendix);
+    CPPUNIT_ASSERT_EQUAL(s0.rawContent(), appendix.rawContent());
+    CPPUNIT_ASSERT_EQUAL(s0, appendix);
 
-    // append() has a shortcut for assignment-to-empty
-    // if compiler uses bitwise copy wrongly the ID would copy too
-    auto oldIdEmpty = empty.getId();
-    empty.append(s2);
-    CPPUNIT_ASSERT(empty.getId() != s2.getId());
-    CPPUNIT_ASSERT_EQUAL(oldIdEmpty, empty.getId());
+    // paranoid: check that the above code can actually detect copies
+    SBuf s1(fox1);
+    s1.append(appendix);
+    CPPUNIT_ASSERT(s1.rawContent() != appendix.rawContent());
+    CPPUNIT_ASSERT(s1 != appendix);
+    CPPUNIT_ASSERT_EQUAL(rawAppendix, appendix.rawContent());
 }
 
 void